Vascular prostheses are used in adults mainly to replace pathological blood vessels in the body and create a bypass or a shunt, and are used in children mainly to create a shunt. Vascular prostheses are thus required to be highly biocompatible and non-toxic, durable and non-degradable in living bodies, flexible, substantially non-permeable to blood, and highly effective in promoting the settlement of adherent vascular endothelial cells.
Vascular endothelial cells constantly produce nitrogen monoxide and prostaglandin to inhibit platelet aggregation. Prostaglandin is a substance that controls platelet function and the coagulation and fibrinolytic system to prevent thrombus formation in the blood vessels. Hence, high effectiveness in promoting the settlement of adherent vascular endothelial cells is a very important characteristic of vascular prostheses.
Conventional textile vascular prostheses are typically made of a woven or knitted fabric of chemical fibers such as polyester. Many of them are made of a very high density woven or knitted fabric, i.e., a tightly woven or knitted fabric to prevent leakage of blood through their walls and maintain their shapes. However, conventional textile vascular prostheses suffer from slow and uneven formation of a vascular endothelial cell layer. That is, in conventional textile vascular prostheses, thick fibers are tightly woven or knitted, which provides only a few scaffolds for formation of a vascular endothelial cell layer. In addition, even though some cells adhere to the inner wall, most of them tend to be easily washed away by the blood flow, which may result in formation of an occluding thrombus in a narrow blood vessel in the periphery.
Various proposals have been made to enhance the settlement of adherent vascular endothelial cells in vascular prostheses. One of the proposals is, for example, a vascular prosthesis having raised microfibers of 0.5 denier or less on the inner wall as described in JP 61-4546 B. Another proposal is a vascular prosthesis having raised microfibers of 0.5 denier or less on the inner wall and/or the outer wall and comprising a ground structure made from a ground yarn containing fibers of 1.0 denier or more as described in JP 61-58190 B.
However, formation of raised microfibers on the inner wall, as described in JP '546 and JP '190, does not sufficiently enhance the settlement of adherent cells. The raised fibers may inversely inhibit the growth of the adherent cells.
JP 2011-245283 A describes a microfiber woven fabric to be used for a stent graft. However, use of that woven fabric for a vascular prosthesis without applying any modifications does not sufficiently improve the settlement of adherent cells, the leakage of blood or kink resistance. JP 2012-139498 A describes a woven fabric with good biocompatibility. The woven fabric does not adversely affect the living body. However, the woven fabric contains no microfibers and, therefore, use of the woven fabric for a vascular prosthesis without applying any modifications does not sufficiently improve the settlement of adherent cells, the leakage of blood or kink resistance.
It could therefore be helpful to provide a vascular prosthesis having various properties required of it and is highly effective in promoting settlement of adherent vascular endothelial cells.